Seizures occurring during a febrile illness affect 2-4% of all children, making them by far the most common form of convulsive disorder. Apart from the observations that children six months to three years of age and those with a family history of febrile seizures are at increased risk, little is known about why some children are affected while others are spared. The work proposed here would continue and expand a case-control study of febrile seizures which was initiated with funding from a private foundation. The study's purposes are: (1) to determine the importance of certain family and maternal characteristics, perinatal exposures, and early childhood events as risk factors for febrile seizures; and (2) to determine the degree to which different clinicals subtypes of febrile seizures have different risk factors. Febrile seizure cases are identified through a surveillance system in twenty Western Washington medical centers and through referrals from area pediatricians. For each case, a control child is chosen from among children born at the same hospital within one week of the case's birth, using Washington state birth certificate files. The mother of each case or control is interviewed by telephone about the family's health history, her own reproductive history, her pregnancy with the study child, delivery events, birth status of the child, and early childhoood health events. Additional data about perinatal events will be obtained from the hospital record of the child's birth. In a second telephone contact, the reliability of information obtained in the initial interview is checked, and additional family history data are obtained. Analyses will employ both traditional methods for analysis of matched case-control data and conditional logistic regression to evaluate each exposure's association with febrile seizure risk, to control for confounding factors, and to assess how the effect of one risk factor depends on the presence or absence of another. The study is expected to yield useful information about the etiology of such seizures, to identify potentially modifiable risk factors, and to provide information which allows clinicians to identify the high risk child in order to furnish anticipatory guidance to parents.